Research On Wafer-level-packaging Silicon Resonant Accelerometer

Silicon resonant accelerometer(SRA)is a kind of micro electromechanical inertial instrument with high precision potential.Its basic principle is that the change of resonant structure stiffness under the action of axial acceleration causes the change of resonance frequency of harmonic oscillator.The input acceleration is measured by measuring the frequency change.Silicon based resonant accelerometers have the advantages of high reliability,long life,small volume and light weight.At the same time,frequency signal output makes them have high theoretical accuracy,so it has become one of the important directions of the development of MEMS inertial instruments.In this paper,the structure design and technology of silicon-based resonant accelerometer,system design,digital measurement and control circuit and other key technologies are studied.The main contents are as follows:The working mechanism of silicon-based resonant accelerometer is studied,the force-frequency output equation is derived,the dynamic model of sensitive structure is established,and the system-level modeling and analysis based on Simulink are carried out,and the driving and detecting mode of harmonic oscillator is analyzed.The scheme of driving detection structure is determined.In view of the deficiency in the structural design of resonant accelerometers at present,a two-layer structural design scheme of silicon-based resonant accelerometers is proposed,and the main modes of the structures are simulated and analyzed by using ANSYS finite element analysis software.The full range simulation and temperature simulation are also carried out.Wafer level packaging technology and microsystem stress matching technology for silicon based resonant accelerometers are studied.The closed-loop driving control mechanism of resonant tuning fork is studied.Based on the principle of self-excited oscillation,the closed-loop drive control system consists of phase control and amplitude control,which is mainly controlled by phase and supplemented by amplitude control.In this paper,the phase-locked loop scheme is used to analyze the phase-locked loop theoretically,and three amplitude-control schemes are analyzed and compared.Based on the above analysis,the closed-loop drive control system is simulated and analyzed at the Simulink system level.The digital driving and high-precision frequency detection technology of silicon resonant accelerometers are studied.The adaptive digital phase-locked loop(DPLL),high-precision frequency detection and serial communication module are designed with Verilog HDL language.The digital measurement and control circuit is built based on FPGA.The test results show that the digital measurement and control circuit can meet the design requirements of accelerometer response speed and range.The test results show that the startup time of the prototype is less than 100 ms,the stability of zero bias is 25.496g(1?),the repeatability of zero bias is 35.384 g,and the scale factor is 197.437 Hz/g.